In-situ Spectroscopic Investigations of High Energy Li-S Batteries Based on New Carbon Cathodes

高能量密度Li-S电池的成功设计对于显著改进现有电池技术，推动环保汽车发展具有挑战性的前景。锂硫电池的能量密度是现有锂离子电池的三倍，具有快速充放电循环的高可逆性和数千次循环的使用寿命。最近，基于电池设计的新方法，我们已经能够开发出具有相对高能量密度和超过50次循环稳定性的Li-S测试电池。然而，活性硫的绝缘性、多硫化物的溶解和氧化还原穿梭现象、体积膨胀、硫化物的电极钝化等限制了锂硫电池性能的问题仍有待解决。在这个项目中，我们将开发新型复合阴极、保护膜和新型电解质，以提高锂电池的性能。由于持续过程的复杂性，我们认为有必要对充电和放电过程进行系统和基础的研究。因此，我们建议使用复杂的表征技术，即近边缘x射线吸收精细结构（NEXAFS）光谱，拉曼光谱和电子自旋共振，其中电池内不同位置的化学修饰在充放电过程中可以被原位跟踪，并检测自由基的形成。因此，单质硫，特别是多硫分布和动力学将被确定，允许特定优化的细胞。在我们的多学科联盟中，新型聚合物基多孔阴极材料的开发，先进电解质的配方以及实验和理论水平上的电化学性能优化将通过三方合作伙伴的共同努力实现。应用方面将与一家领先的电池生产公司密切联系进行讨论。

The successful design of Li-S batteries with high energy density has the challenging perspective to significantly improve existing battery technology and to boost the development of environmentally friendly automotive development. Li-S batteries could triple the energy density of existing Li-ion batteries combined with high reversibility of fast charging-discharging cycles and lifetime of thousands of cycles. Recently, based on novel approaches for battery design we have been able to develop Li-S test cells with relatively high energy density and stability over 50 cycles. There are, however still problems to be solved related to the insulating nature of active sulfur, polysulfide dissolution and redox shuttle phenomena, volume expansion, electrode passivation by sulfides etc. that limits the performance of Li-S batteries. In this project we will develop novel composite cathodes, protective membranes and new electrolytes which will allow improvement of the performance of Li-S batteries. Due to the complex nature of ongoing processes we believe that systematic and basic studies of charging and discharging processes are necessary. Therefore, we propose to use sophisticated characterisation techniques, i.e. near edge X-ray absorption fine structure (NEXAFS) spectroscopy, Raman spectroscopy and electron spin resonance, where chemical modifications at different locations inside the cell during charging and discharging may be followed in situ and radical formation is detected. Thus, elemental sulfur and in particular polysulfide distribution and kinetics will be determined, allowing specific optimisation of the cells. In our multidisciplinary consortium, development of new polymer-based porous cathode materials, formulation of advanced electrolytes and optimisation electrochemical performance at experimental and theoretical levels will be realised by the combined efforts of the three partners. Application aspects will be discussed in close contact with a leading battery producing company.